Digital audio is recorded and stored in electronic equipment. If the audio is needed in court, the original device that created the recording must be identified and kept in a chain of custody. The only exception is when both parties involved in the litigation agree that a copy is sufficient. If there is doubt in the authenticity, the audio expert must refer to the original to support the authentication of the audio evidence.
The reason is that the audio copy has been removed from its original environment and is vulnerable to alteration. In addition, if a computer created the original recording, additional information can be examined by the audio expert such as file creation, last accessed and other computer forensic information that can support the audio evidence authenticity.
If the original audio recording was created in a digital pocket recorder (which many law enforcement officials use) then that original pocket recorder must maintain a chain of custody and become the original evidence. Any external copy created by a number of methods and played outside of the digital pocket recorder is a copy. Unless an audio expert can authenticate the copy (which can be done once the original has been examined) it cannot be used in a court proceeding. If the audio copy has been authenticated by an expert, than it will be easier to play and amplify in the court for a judge and jury.
I have testified in criminal cases for the defense when the client swore under oath that the audio recording had been altered and did not represent the facts as they occurred. Now it?s their word against the other side and when the court has to decide, the prosecution most always, will prevail.
If you have had an experience with audio evidence and would like to share your story, please comment on this post and your story will be heard.